Wireshark Lab: DNS

Computer Networking: A Top-

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Version: 2.0 down Approach, 4 edition.

© 2007 J.F. Kurose, K.W. Ross. All Rights Reserved

As described in Section 2.5 of the textbook, the Domain Name System (DNS) translates

hostnames to IP addresses, fulfilling a critical role in the Internet infrastructure. In this

lab, we’ll take a closer look at the client side of DNS. Recall that the client’s role in the

DNS is relatively simple – a client sends a query to its local DNS server, and receives a

response back. As shown in Figures 2.21 and 2.22 in the textbook, much can go on

“under the covers,” invisible to the DNS clients, as the hierarchical DNS servers

communicate with each other to either recursively or iteratively resolve the client’s DNS

query. From the DNS client’s standpoint, however, the protocol is quite simple – a query

is formulated to the local DNS server and a response is received from that server.

Before beginning this lab, you’ll probably want to review DNS by reading Section 2.5 of

the text. In particular, you may want to review the material on local DNS servers, DNS

caching, DNS records and messages, and the TYPE field in the DNS record.

1. nslookup

In this lab, we’ll make extensive use of the nslookup tool, which is available in most

Linux/Unix and Microsoft platforms today. To run nslookup in Linux/Unix, you just type

the nslookup command on the command line. To run it in Windows, open the Command

Prompt and run nslookup on the command line.

In it is most basic operation, nslookup tool allows the host running the tool to query any

specified DNS server for a DNS record. The queried DNS server can be a root DNS

server, a top-level-domain DNS server, an authoritative DN